Field of the Invention
The invention relates to a packaging article for containing and holding food products, which article comprises one or more chambers defined by walls, bottom(s) and lid(s) where the walls, bottom(s) and lid(s) have barrier means for limiting permeability of oxygen through the article and into the one or more chambers and comprising an oxygen scavenger in at least the walls, bottom(s) or lid(s).
The invention further relates to a method of manufacturing a packaging article for containing and holding food products, which article comprises one or more chambers defined by walls, bottom(s) and lid(s) where the walls, bottom(s) and lid(s) have barrier means for limiting permeability of oxygen through the article and into the one or more chambers.
The Prior Art
It is known to produce articles for containing food products from different types of plastic. Plastics are relatively easy to mould into a desired configuration.
It is also known to produce articles for containing food products from plastic sheet, film or laminated film.
The plastic sheets or film are made in an extrusion process. The sheet or film material is converted into plastic bags or trays which can be filled with oxygen-sensitive food.
These types of trays or containers do not leave the manufacturer much liberty of producing or designing a more welcoming appearance as well as the possibility of puncture of the sheet or film exists and thereby significantly shortening the storage life of the food product, sometimes even without the puncture being noticed.
Therefore it is desirable to be able to manufacture a packaging article with greater liberty of producing or designing and a more welcoming appearance together with a more stable structure preventing unintended puncturing of parts of the packaging article.
This can be done by injection moulding the packaging article from a polypropylene which gives fine results with regards to designing and a more welcoming appearance as well as an article more resistant for instance to punctures. Unfortunately, the oxygen permeability for polypropylene is not satisfactory. When used in combination with food products, it is advantageous to have a packaging article with adequate barrier properties.
To give polypropylene better properties with respect to forming an oxygen barrier, another material has been added to the polypropylene before moulding. A material such as ethylene vinyl alcohol (EVOH) has been used to achieve the desired barrier properties. Other barrier materials could be SiOx, a coating of PVDc or a compound of a special nylon such as MXD6 mixed into the basis material.
Further, polypropylene makes it possible to perform a heat treatment of the food product placed in the packaging article, which is not possible with all plastics.
Oxygen contained in the interior of the packaging article together with a food product is unwanted, since the oxygen contributes to the putrefaction of the food product.
To avoid such a situation or ensure a better storage life of the food product kept in the packaging article, different methods have been tested. One method is to put an oxygen scavenger into the packaging article, either by simply putting an oxygen-scavenging member into the package together with the food product or by adding the oxygen scavenger to the plastic material used to manufacture the packaging article.
An oxygen scavenger is a substance or material capable of absorbing oxygen by a chemical reaction and thereby able to remove or reduce the content of oxygen from an enclosure.
US 2003/0091769 A1 describes a multilayer preform and container with coextruded liner. Here, the packaging article is manufactured as a multilayer preform, where one or more of the layers comprise an oxygen scavenger.
The problem arising when using a preform to manufacture an article is that the preform probably will be stored for a longer period. If nothing is done to prohibit the oxygen scavenger from starting its oxygen-absorbing reaction, it is possible that the scavenging action will not be sufficient at the time the preform is moulded into its final shape and ready to be filled with for example beverages.
To prevent this reaction from starting before the scavenging property is needed, the scavenger can be sandwiched between at least two barrier layers.
New Technique
To provide a packaging article with a more welcoming appearance and a greater liberty of producing such trays or containers together with improved scavenging and barrier properties, a new tray or container for food products and a new method of manufacturing such a tray or container are developed. This is achieved by the invention by providing a packaging article that comprises oxygen-scavenging means, which oxygen-scavenging means together with a second plastic material is moulded into a cavity in a first plastic material forming walls, bottom(s) and lid(s) of the packaging article, which first plastic material is suitable for contact with food products.
The first and second plastic materials are in most cases different plastic materials, but it is possible to use the same plastic material as both first and second material. The advantage of using a different plastic material as the second plastic material is that it is not necessary to use a plastic material suitable for contact with food products, since the second plastic material is embedded in or surrounded by the first plastic material.
Further, a method of manufacturing such a packaging article is developed.
This method is an expedient way of manufacturing a packaging article according to the invention.
This is achieved by placing an In-Mould-Label film (IML film) with a barrier film or coating in an injection mould and thereafter injecting a polypropylene into the mould. The polypropylene is injected into the mould in such a way that an oxygen scavenger is surrounded by polypropylene material and the oxygen scavenger is situated on the inner side of the In-Mould-Label, but not necessarily adjacent to the In-Mould-Label.
By the method the article in the form of a high barrier packaging is finished in one injection moulding cycle comprising the following three process steps:                An oxygen barrier film with or without decoration is placed in the mould.        A first plastic material suitable for contact with food products is injected into the closed mould where the barrier film is placed. The mould is partly filled in this step.        A second plastic material containing an oxygen scavenger (3) is injected into the mould until the mould is filled, whereby the oxygen scavenger (3) is surrounded by the first plastic material (2) suitable for contact with food products.        
This method using In-Mould-Labelling technology makes the oxygen barrier film an integrated part of the injection moulded packaging, where the injected plastic is forming a sandwich structure with a layer of a second plastic material containing an oxygen scavenger sealed between two layers of a first plastic material intended for contact with food products.
When the first plastic material, which is a kind of polypropylene, is injected into the mould, the outer part of the plastic material is cooled by contact with the inner surfaces of the mould and the part of the plastic material pointing in the direction away from the inner surfaces (the inner part of the mould cavity) is still flowing through the mould. This action can be described as “rolling out a carpet” on both sides of the material at a time.
Since the IML film is placed in the mould before injecting the polypropylene, the polypropylene will attach to the IML film during partly filling the mould.
After this step a cavity in the polypropylene is achieved, which cavity is filled with a second plastic material comprising an oxygen scavenger.
Hereby a high barrier plastic packaging is achieved, which is made by injection moulding. This type of packaging combines the excellent barrier properties in film and sheet material with the high quality and design freedom of injection moulded packaging and comprising an oxygen scavenger.
This method using In-Mould-Labelling technology makes the barrier film an integrated part of the injection moulded packaging, where the injected plastic is forming an inner side intended for contact with food products and with the external side formed of an In-Mould-Label. Further, the oxygen scavenger is embedded in the polypropylene in such a way that the scavenger is not in direct contact with the food products contained in the packaging article in use.
A suitable material for the barrier as mentioned previously could be EVOH.
According to an embodiment of the invention, an effective oxygen-scavenging high barrier packaging article is provided by having oxygen scavenging means moulded into the inner part of the walls, bottom(s) or lid(s) of the packaging article.
According to an embodiment of the invention, an effective oxygen-scavenging high barrier packaging article is provided by having a packaging article, which on its outer side is provided with barrier properties by In-Mould-Labelling a label comprising a barrier film together with injection moulding the packaging article from a polypropylene.
According to an embodiment of the invention, a high barrier packaging article is provided where the barrier means is embedded in the label.
According to an embodiment of the invention, a high barrier packaging article is provided where the barrier means is chosen from a group consisting of silicium oxide (SiOx) or a coating of silicium oxide (SiOx), a coating of PVDc, a special nylon such as MXD6 mixed into the basis material or of EVOH (ethyl-vinyl-alcohol).
According to an embodiment of the invention, a high barrier packaging article is provided where the barrier surrounds most of or the entire outer area or surface of the packaging article.
According to the invention, a packaging article with embedded oxygen-scavenging means is made in one injection moulding cycle consisting of three process steps.
According to an embodiment of the invention, a packaging article with oxygen scavenging means is made by mixing an oxygen-scavenging material in a plastic material before injecting this mixture into a partly moulded packaging article.